Searching by Functional Groups and Common Heterocyclic Rings

Chemical Abstracts Service, 1993. Reproduced for educational purposes with
permission from CAS, a Division of the
American Chemical Society.

CAS has defined approximately:

160 terms which represent structural features

40 short linear descriptions for common heterocycles

10 functional group class terms

Functional Group and Ring terms are quick and easy to search,
allow you to do general reaction searching, and can be used to
overcome structure search system limits.

While Functional Groups and Ring terms may be used to search
reactants, reagents, and products, they may not be used to search
solvents and catalysts.

Role Qualifiers for Functional Groups

Group is present in the reaction, not that the group definitely
participates in the reaction(s):

Group is in a reactant

/FG.RCT

Group is in a reagent

/FG.RGT

Group is in a product

/FG.PRO

Group has any role

/FG

If Group is involved in the reaction, then use these indexes:

Group on reactant takes part in the reaction

/FG.RXN

Group is formed in the reaction

/FG.FORM

Group is present, but does not participate in the reaction

/FG.NON

Examples:=> s nitrile/fg.pro [to find a nitrile in the product]=> s nitrile/fg.form [to find nitrile formed in the reaction]

Using Multiple Functional Group Search Terms

The (S) Operator

The (S) proximity operator specifies that the reacting functional group is
actually converted to the forming functional group. The definition of
conversion is that at least one atom in the reacting group is still present
in the forming group.

For example, to retrieve only reactions in which a nitrogen atom in the
reacting functional group is converted to a primary amine:=> s azide/fg.rxn (s) primary amine/fg.form

The (S) operator cannot be used with the /FG.RGT, FT.NON, or /FG indexes

Use (S) proximity for the best precision.

The (L) Operator

The (L) proximity operator specifies that the functional groups be in the same
reaction. This is a broader specification than the (S) operator.

The (L) operator may be used with the /FG.RGT, FT.NON, or /FG indexes.

"In the Presence of" Reactions

To look for reactions in the presence of a functional group, we combine reacting,
forming, and non-reacting functional groups using (S) and (L) proximity.

For example, to look for the conversion of an azide to a primary amine in the
presence of a primary alcohol.=> s azide/fg.rxn (s) primary amine/fg.form (l) primary alcohol/fg.non